1. Field of the Invention
The present inventions relates in general to a motor rotor and in particular to a method of manufacturing the rotor structure of the motor.
2. Description of the Related Art
A conventional fan is shown in FIG. 1, including a rotor assembly 1, a stator 2 and a frame 3. The rotor assembly 1 includes a blade structure 11 having a hub 111 and blades 112 disposed around the periphery of the hub 111. A metal shell 12 and a magnet 13 are disposed on the interior side of the hub 111 accordingly. A shaft 113 is placed in the inner center of the hub 111 and a washer 14 is placed on the shaft 113. The stator 2 includes a sleeve 21, a coil 22, an upper insulation spacer 23, an upper pole plate 24, a lower insulation spacer 25, a lower pole plate 26 and a circuit board 27. The sleeve 21 is a hollow tube and a ball bearing 211 is disposed in the upper interior part of the sleeve 21. The lower portion of the sleeve 21 has a self-lubricating bearing 212. Several bushings are placed between the ball bearing 211 and the self-lubricating bearing 212. The upper insulation spacer 23 and the upper pole plate 24 are placed sequentially on the top of coil 22, and then encircling the outer periphery of the sleeve 21. The lower insulation spacer 25, the lower pole plate 26 and the circuit board 27 are also sequentially placed encircling the outer periphery of sleeve 21. Thus, the top surface of the lower insulation spacer 25 contacts the lower end of coil 22. The shaft 113 of the rotor assembly 1 passes through the opening in ball bearing 211 and the self-lubricating bearing 212 and a c-ring 15 is locked at the end of the shaft 113 to connect the rotor assembly 1 and the stator 2. Further, a sensor is disposed on the circuit board 27 for detecting and controlling the magnetic field of the stator 2. Finally, the bottom surface of the stator 2 is connected to the frame 3, thereby completing the fan assembly.
The metal shell 12, however, typically is ring-shaped and formed by molding. In detail, the metal is cut first, and molded in a die-cast. This method is costly and time consuming, and requires a special die for each new different design such that the formed die can not be shared and easily modified.